In recent years, portable electronic devices such as laptop computers or cellular phones have become widespread rapidly with developments of communication systems, and also have increased in performance year after year. In particular, portable devices tend to increase their power consumptions with increase in performance. Therefore, as to a battery which works as a power supply thereof, there has been increasing demand of high energy density, a large output, and the like.
As a battery having a high energy density, a lithium ion battery has been developed and widely used since the 1990s. In the lithium ion battery, as an electrode active material, for example, a lithium-containing transition metal oxide such as lithium manganate or lithium cobaltate is used for a cathode, and carbon is used for an anode. The lithium ion battery uses an insertion reaction of lithium ions into the electrode active material and an elimination reaction of lithium ions from the electrode active material to charge and discharge. Such a lithium ion battery has a high energy density and exhibits excellent cycle performance, and thus the lithium ion battery is used in various kinds of electronic devices represented by cellular phones. However, the lithium ion battery has a low reaction rate of the electrode reaction, and thus extracting a large current seriously deteriorates battery properties. Therefore, the lithium ion battery has drawbacks of having difficulties to produce a large output and also requiring many hours to recharge.
As a storage device that produces a large output, an electric double layer capacitor is known. The electric double layer capacitor can discharge a large current at one time and thereby producing a large output. The electric double layer capacitor also exhibits excellent cycle performance, and has been developed as a backup power supply. However, the electric double layer capacitor is not suitable for a power supply of portable electronic devices because the capacitor has a very low energy density and downsizing of the capacitor is difficult.
For the purpose of obtaining an electrode material that is lightweight and has a high energy density, there has been developed a battery using a sulfur compound or an organic compound as an electrode active material. For example, Patent Document 1 (U.S. Pat. No. 4,833,048) and Patent Document 2 (Japanese Patent No. 2,715,778) disclose a battery using an organic compound having a disulfide bond for a cathode. This battery uses an electrochemical oxidation-reduction reaction that involves forming and dissociating disulfide bonds as the principle on which the battery operates. The battery is composed of an electrode material containing sulfur or carbon as its main component, both of which are elements of low specific gravity, thereby achieving some effects as a large capacity battery having a high energy density. However, the battery has a drawback that its capacity tends to decrease through charging and discharging cycles because the dissociated bonds have a low efficiency to form the bonds again and the electrode active material diffuses into an electrolyte solution.
In addition, as a battery using an organic compound, there is proposed a battery using a conductive polymer as an electrode material. This battery uses doping and undoping reactions of electrolyte ions for the conductive polymer as the principle on which the battery operates. The doping reaction is defined as a reaction of stabilizing charged radicals generated by oxidation or reduction of the conductive polymer by counter ions. Patent Document 3 (U.S. Pat. No. 4,442,187) discloses a battery using such a conductive polymer as a cathode or anode material. This battery consists of only sulfur and carbon both of which are elements of low specific gravity, and was expected as a large capacity battery. The conductive polymer, however, has a property that charged radicals generated by oxidation or reduction of the conductive polymer are delocalized over a wide region of π-electron conjugated system and the charged radicals interact each other to cause electrostatic repulsion or elimination of the radicals. This property restricts the generation of charged radicals, namely the concentration of doping, and thus limits the capacity of a battery. For example, it is reported that a battery using polyaniline as a cathode has a doping ratio of 50% or less, and a battery using polyacetylene as a cathode has a doping ratio of 7%. The battery using a conductive polymer as an electrode material achieves some effects in weight reduction, however, a battery having a high energy density has not been obtained.
As a battery using an organic compound as an electrode active material, there is proposed a battery using an oxidation reduction reaction of a radical compound. For example, Patent Document 4 (Japanese Patent Application Laid-Open No. 2002-151084) discloses an organic radical compound such as a nitroxide radical compound, an aryloxy radical compound, and a polymer having a specific amino triazine structure as an active material; and a battery using the organic radical compound as a positive or anode material. Furthermore, Patent Document 5 (Japanese Patent Application Laid-Open No. 2002-304996) discloses a storage device that uses particularly a compound having a cyclic nitroxide structure among nitroxide compounds as an electrode active material. In addition, the polyradical compound used as the electrode active material therein is synthesized by reacting 2,2,6,6-tetramethyl piperidine methacrylate with azobisisobutyronitrile, which is a polymerization initiator to conduct polymerization, subsequently oxidizing the polymer with m-chloro perbenzoic acid. On the other hand, Patent Document 6 (Japanese Patent Application Laid-Open No. 2002-313344) discloses a battery using a nitroxyl radical polymer, which is a polyradical compound, as a binder for an electrode.
By the way, as a method for synthesizing a vinyl ether monomer, known methods are: a method of reacting acetylene with an corresponding alcohol at a high temperature (180 to 200° C.) under increased pressure (about 20 to 50 atm) in the presence of catalytic amounts of potassium hydroxide and sodium hydroxide (Non-Patent Document 1: W. Reppe et al, Annalen der Chemie (Ann.), vol. 601 (1956), p. 81-111); a method of heating and refluxing an corresponding alcohol and alkyl vinyl ether in the presence of mercuric acetate catalyst (Non-Patent Document 2: Warren H. et al, Journal of The American Chemical Society, vol. 79 (1957), p. 2828-2833); and a method of heating and refluxing an corresponding alcohol and vinyl acetate in the presence of iridium catalyst (Non-Patent Document 3: Yasutaka Ishii et al, Journal of The American Chemical Society, vol. 124 (2002), p. 1590-1591; and Patent Document 7: Japanese Patent Application Laid-Open No. 2003-73321).    Patent Document 1: U.S. Pat. No. 4,833,048    Patent Document 2: Japanese Patent No. 2,715,778    Patent Document 3: U.S. Pat. No. 4,442,187    Patent Document 4: Japanese Patent Application Laid-Open No. 2002-151084    Patent Document 5: Japanese Patent Application Laid-Open No. 2002-304996    Patent Document 6: Japanese Patent Application Laid-Open No. 2002-313344    Patent Document 7: Japanese Patent Application Laid-Open No. 2003-73321    Non-Patent Document 1: W. Reppe et al, Annalen der Chemie (Ann.), vol. 601, p. 81-111 (1956)    Non-Patent Document 2: Warren H. et al, Journal of The American Chemical Society, vol. 79, p. 2828-2833 (1957)    Non-Patent Document 3: Yasutaka Ishii et al, Journal of The American Chemical Society, vol. 124, p. 1590-1591 (2002)